(1) Field of the Invention
The present invention relates to a valve control structure for a working vehicle, and more particularly to a valve control structure in which one of two valves is controlled by rocking movements in a first direction of a control lever rockable crosswise and the other valve by rocking movements in a second direction of the control lever. This valve control structure includes means to interchange the controls of the two valves with respect to the rocking directions of the control lever.
(2) Description of the Prior Art
This type of valve control structure is disclosed, for example, in U.S. Pat. No. 4,541,161. According to the known structure, a relay device in mounted in a connecting rod mechanism interconnecting valves and a mechanism for converting rocking movements of a control lever into linear movements. Valve control lines are changeable with respect to rocking directions of the control lever by changing an attachment arrangement of rods between the rocking/linear movement converting mechanism and the relay device and between the valves and the relay device.
Another known example is disclosed in the Japanese patent application laid open under No. 60-211522 (which corresponds to the British patent application published under No. GB No. 2159492A). The control structure disclosed therein comprises a connecting rod mechanism including a cam type cross-over switch mechanism and mounted between a rocking/linear movement converting mechanism and valves. The relay device and the cross-over switch mechanism both have very large constructions, which are not only expensive to manufacture but require a large accommodating space. Furthermore, the relay device and the cross-over switch mechanism are mounted between the rocking/linear movement converting mechanism and the valves, and require connecting rods to be connected to the converting mechanism and connecting rods to be connected to the valves. This results in a complicated interlocking structure involving many constituent elements. It is troublesome and time-consuming to assemble the interlocking structure by incorporating one element after another into a vehicle body during a vehicle assembly process. Therefore, the vehicle is assembled and manufacture with a very poor efficiency.